The provision of thermally and/or electrically insulating coatings of epoxy resins on steel pipe sections, for example, which are intended to be used to form fluid conducting pipelines, either above or below the ground, is known. Customarily, the process involves the spraying of the epoxy resin in powder form onto steel pipe electrostatically. After abrasive cleaning of the pipe surface, e.g. by shot blasting, the metal pipe is heated, given an electrical charge, and epoxy resin powder charged oppositely to the pipe is applied to the pipe by spraying, so that the powder adheres electrostatically to the pipe surface. The coating cures on the hot pipe thereon. The epoxy resin powder which does not adhere to the pipe surface after spraying is collected and returned to the epoxy powder storage hopper to be recycled. One electrostatic powder coating process of this type is described in U.S. Pat. No. 3,904,346 dated Sept. 9, 1975.
In the case of an epoxy coated steel pipe or the like in which the resin coating provides a moisture impermeable barrier around the pipe, it is important that the coating should withstand without rupture any impact to which it would normally be subjected, as in the subsequent handling of the pipe, or its installation and use in the field, or in the application of concrete cladding in some cases for particular applications. The coating is normally very thin, typically a few mils, and cannot usefully be made thicker as this would result in its becoming brittle.